diff options
Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 59 |
1 files changed, 41 insertions, 18 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index bead931529..b5bd24d027 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -663,11 +663,11 @@ By default, associations look for objects only within the current module's scope module MyApplication module Business class Supplier < ApplicationRecord - has_one :account + has_one :account end class Account < ApplicationRecord - belongs_to :supplier + belongs_to :supplier end end end @@ -679,13 +679,13 @@ This will work fine, because both the `Supplier` and the `Account` class are def module MyApplication module Business class Supplier < ApplicationRecord - has_one :account + has_one :account end end module Billing class Account < ApplicationRecord - belongs_to :supplier + belongs_to :supplier end end end @@ -697,14 +697,14 @@ To associate a model with a model in a different namespace, you must specify the module MyApplication module Business class Supplier < ApplicationRecord - has_one :account, + has_one :account, class_name: "MyApplication::Billing::Account" end end module Billing class Account < ApplicationRecord - belongs_to :supplier, + belongs_to :supplier, class_name: "MyApplication::Business::Supplier" end end @@ -811,6 +811,7 @@ When you declare a `belongs_to` association, the declaring class automatically g * `build_association(attributes = {})` * `create_association(attributes = {})` * `create_association!(attributes = {})` +* `reload_association` In all of these methods, `association` is replaced with the symbol passed as the first argument to `belongs_to`. For example, given the declaration: @@ -828,6 +829,7 @@ author= build_author create_author create_author! +reload_author ``` NOTE: When initializing a new `has_one` or `belongs_to` association you must use the `build_` prefix to build the association, rather than the `association.build` method that would be used for `has_many` or `has_and_belongs_to_many` associations. To create one, use the `create_` prefix. @@ -840,10 +842,10 @@ The `association` method returns the associated object, if any. If no associated @author = @book.author ``` -If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload` on the parent object. +If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload_association` on the parent object. ```ruby -@author = @book.reload.author +@author = @book.reload_author ``` ##### `association=(associate)` @@ -966,13 +968,12 @@ side of the association. Counter cache columns are added to the containing model's list of read-only attributes through `attr_readonly`. ##### `:dependent` -Controls what happens to associated objects when their owner is destroyed: +If you set the `:dependent` option to: -* `:destroy` causes the associated objects to also be destroyed. -* `:delete_all` causes the associated objects to be deleted directly from the database (callbacks are not executed). -* `:nullify` causes the foreign keys to be set to `NULL` (callbacks are not executed). -* `:restrict_with_exception` causes an exception to be raised if there are associated records. -* `:restrict_with_error` causes an error to be added to the owner if there are associated objects. +* `:destroy`, when the object is destroyed, `destroy` will be called on its +associated objects. +* `:delete`, when the object is destroyed, all its associated objects will be +deleted directly from the database without calling their `destroy` method. WARNING: You should not specify this option on a `belongs_to` association that is connected with a `has_many` association on the other class. Doing so can lead to orphaned records in your database. @@ -1161,6 +1162,7 @@ When you declare a `has_one` association, the declaring class automatically gain * `build_association(attributes = {})` * `create_association(attributes = {})` * `create_association!(attributes = {})` +* `reload_association` In all of these methods, `association` is replaced with the symbol passed as the first argument to `has_one`. For example, given the declaration: @@ -1178,6 +1180,7 @@ account= build_account create_account create_account! +reload_account ``` NOTE: When initializing a new `has_one` or `belongs_to` association you must use the `build_` prefix to build the association, rather than the `association.build` method that would be used for `has_many` or `has_and_belongs_to_many` associations. To create one, use the `create_` prefix. @@ -1190,10 +1193,10 @@ The `association` method returns the associated object, if any. If no associated @account = @supplier.account ``` -If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload` on the parent object. +If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload_association` on the parent object. ```ruby -@account = @supplier.reload.account +@account = @supplier.reload_account ``` ##### `association=(associate)` @@ -1443,6 +1446,7 @@ When you declare a `has_many` association, the declaring class automatically gai * `collection.build(attributes = {}, ...)` * `collection.create(attributes = {})` * `collection.create!(attributes = {})` +* `collection.reload` In all of these methods, `collection` is replaced with the symbol passed as the first argument to `has_many`, and `collection_singular` is replaced with the singularized version of that symbol. For example, given the declaration: @@ -1471,11 +1475,12 @@ books.exists?(...) books.build(attributes = {}, ...) books.create(attributes = {}) books.create!(attributes = {}) +books.reload ``` ##### `collection` -The `collection` method returns an array of all of the associated objects. If there are no associated objects, it returns an empty array. +The `collection` method returns a Relation of all of the associated objects. If there are no associated objects, it returns an empty Relation. ```ruby @books = @author.books @@ -1609,6 +1614,14 @@ The `collection.create` method returns a single or array of new objects of the a Does the same as `collection.create` above, but raises `ActiveRecord::RecordInvalid` if the record is invalid. +##### `collection.reload` + +The `collection.reload` method returns a Relation of all of the associated objects, forcing a database read. If there are no associated objects, it returns an empty Relation. + +```ruby +@books = @author.books.reload +``` + #### Options for `has_many` While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_many` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: @@ -1965,6 +1978,7 @@ When you declare a `has_and_belongs_to_many` association, the declaring class au * `collection.build(attributes = {})` * `collection.create(attributes = {})` * `collection.create!(attributes = {})` +* `collection.reload` In all of these methods, `collection` is replaced with the symbol passed as the first argument to `has_and_belongs_to_many`, and `collection_singular` is replaced with the singularized version of that symbol. For example, given the declaration: @@ -1993,6 +2007,7 @@ assemblies.exists?(...) assemblies.build(attributes = {}, ...) assemblies.create(attributes = {}) assemblies.create!(attributes = {}) +assemblies.reload ``` ##### Additional Column Methods @@ -2004,7 +2019,7 @@ WARNING: The use of extra attributes on the join table in a `has_and_belongs_to_ ##### `collection` -The `collection` method returns an array of all of the associated objects. If there are no associated objects, it returns an empty array. +The `collection` method returns a Relation of all of the associated objects. If there are no associated objects, it returns an empty Relation. ```ruby @assemblies = @part.assemblies @@ -2116,6 +2131,14 @@ The `collection.create` method returns a new object of the associated type. This Does the same as `collection.create`, but raises `ActiveRecord::RecordInvalid` if the record is invalid. +##### `collection.reload` + +The `collection.reload` method returns a Relation of all of the associated objects, forcing a database read. If there are no associated objects, it returns an empty Relation. + +```ruby +@assemblies = @part.assemblies.reload +``` + #### Options for `has_and_belongs_to_many` While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_and_belongs_to_many` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: |